1. Field of the Invention
The present invention relates to a liquid crystal display device substrate, and more particularly, to a color filter substrate and method of fabricating a color filter substrate for a liquid crystal display device.
2. Discussion of the Related Art
In general, a liquid crystal display (LCD) device includes upper and lower substrates with a liquid crystal material layer disposed therebetween. One of the upper or lower substrates commonly includes a color filter layer for displaying color images. The color filter layer may commonly include sub-color filters of red (R), green (G), and blue (B). The color filter layer is formed by various methods including a dyeing method, an electro-deposition method, a pigment dispersion method, and a printing method, for example. In general, the pigment dispersion method is commonly used because it forms a fine pattern.
FIG. 1 is a cross-sectional view of a liquid crystal display device according to the related art. In FIG. 1, the LCD device includes first and second substrates 31 and 11, which are spaced apart and face each other, a liquid crystal material layer 50 is interposed between the first and second substrates 31 and 11, and a thin film transistor “T” is formed on the inner surface of the first substrate 31. A pixel electrode 32 of a transparent conducting material is formed on the first substrate 31, and the pixel electrode 32 is disposed at a pixel region “P.” The pixel electrode 32 is connected to the thin film transistor “T,” which functions as a switching device for transmitting signals to the pixel electrode 32. A first alignment layer 34 covers the thin film transistor “T” and the pixel electrode 32. Although not shown, the thin film transistor “T” includes a gate electrode connected to a scanning line, an active layer formed on the gate electrode, and source and drain electrodes separated apart from each other on the active layer, wherein a portion of the active layer exposed between the source and drain electrodes forms a channel of the thin film transistor.
In FIG. 1, a black matrix 12 is formed on the inner surface of the second substrate 11, and a color filter 14 is formed on the black matrix 12. The color filter 14 includes the three sub-color filters of red (R), green (G), and blue (B) disposed in the pixel region “P” and overlaps the black matrix 12. A common electrode 18 made of a transparent conducting material is formed on the color filter 14, and a second alignment layer 20 is formed on the common electrode 18. The liquid crystal material layer 50 is disposed between the first alignment layer 34 and the second alignment layer 20, wherein preliminary alignment of liquid crystal molecules of the liquid crystal material layer 50 is dependent upon characteristics of the alignment layers 34 and 20. Then, first and second polarization films 36 and 22 are arranged outer surfaces of the first and second substrates 31 and 11, respectively, wherein transmission axes of the first and second polarization films 36 and 22 are perpendicular to each other.
FIGS. 2A to 2D are cross-sectional views of a fabrication method for a color filter substrate of the liquid crystal display device of FIG. 1 according to the related art. In FIG. 2A, the black matrix 12 is formed on the second transparent substrate 11, wherein the black matrix 12 has an opening corresponding to the pixel region “P.” The second transparent substrate 11 may be made of glass, and the black matrix 12 may be made of an inorganic material such as chromium (Cr), Cr/CrOx, or an organic material that includes carbon. Here, the black matrix 12 material includes an inorganic material such as chromium and is formed by a sputtering method under vacuum conditions, whereby the manufacturing process is complicated and expensive. Conversely, forming the black matrix 12 of the organic material is advantageous due to the relatively short manufacturing process, low cost, and high visibility. Accordingly, the organic material is commonly selected for the black matrix 12.
In FIG. 2B, the color filter layer 14 is formed within the pixel region “P” on the second transparent substrate 11 having the black matrix 12. The color filter layer 14 overlaps the black matrix 12, and includes three sub-color filters 14a, 14b, and 14c of red, green, and blue, respectively, and each of the sub-color filters correspond to each of the pixel regions “P.” The color filter layer 14 may be formed by the pigment dispersion method, which includes steps of coating a photosensitive color resin on a substrate, exposing the color resin to a light, and developing the color resin.
In FIG. 2C, the common electrode 18 and the alignment layer 20 are subsequently formed on the color filter layer 14. The common electrode 18 is formed of a transparent conducting material, and the alignment layer 20 is formed of polyimide. Thus, a color filter substrate is completed.
In FIG. 2D, the polarization film 22 is formed on the outer side of the color filter substrate. Although not shown, the polarization film 22 is formed after forming a liquid crystal cell by aligning and attaching the color filter substrate and an array substrate. The array substrate is fabricated by processes of deposition and patterning a thin film using several masks; injecting liquid crystal materials; and sealing.
In the fabrication method of FIGS. 2A to 2D, as the color filter substrate is fabricated using a photolithographic process, the second transparent substrate 11 is chemically processed. Accordingly, the second transparent substrate 11 must be formed of specific materials that are chemically resistant. In addition, an overcoat layer (not shown) may be formed on the color filter layer 14 to flatten an inner surface of the second transparent substrate 11. Accordingly, a total number of manufacturing processes is increased,. thereby increasing manufacturing costs.